Aerial Photography and Visualisation for Built Heritage - PhD Portfolio by Kieran Baxter
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Friday, 21 October 2011

Reconstructing the Crannog Roof from KAP to 3D

I selected 114 photographs of the Crannog from different angles to generate a point cloud of 84,000 vertices. This was cleaned a little and then poisson surface reconstruction applied to generate this mesh:

The spatial accuracy of this geometry makes it easy to texture by projecting the original photographs onto the surface. This turnaround was textured using just one straight-down frame:

There are more photograhs, and therefore data acuarcy, on one side than the other. Of the more subtle features which have survived in the photogrammetry data you can make out the archway above the door and verticle ridges which relate to the suporting structure underneath the thatch.

Monday, 17 October 2011

Photographing the Iron Age Roof at Loch Tay's Crannog

The Scottish Crannog Centre is a reconstruction of a 2600 year old roundhouse built out on the waters of Loch Tay. It is of particular interest to my project as the roof is of a similar structure to what may have covered the northern brochs.

My aim was to capture the detail of the roof in different lighting conditions and from enough angles to attempt photogrammetry. Because of the surrounding trees and water I flew the kite from a small boat, skillfully piloted by my brother Dan. After several passes, 2 hours and over 4000 frames we got the angles I was looking for.

The Crannog was built in 1994 based on underwater excavations of Oakbank, a site further along the loch. For the most part traditional methods and materials were used in the reconstruction although it is worth mentioning that the original roof was most likely thatched with bracken rather than the reed thatch used in the contemporary version. The bracken would probably have appeared rougher and darker and would have decomposed faster. The spread of lichen (white dots) on the shaded north side is clearly visible after just over 15 years.

Taking a tour of the Crannog you can get a feel for the life and atmosphere in this kind of settlement. There is no chimney, instead smoke would filter slowly through the roof, helping to preserve meat which would be hung there. A short video and history of the Crannog can be found here.

Wednesday, 12 October 2011

Climate Averages for Shetland & Orkney

This data derived from the Met Office website shows monthly averages up to the year 2000. I have divided the hours of sunlight by the hours of daylight to get a percentage likelyhood that at any given moment during the day the sun will be out. Throughout the year Shetland looks to expect around 2.5% less sun than Orkney as well as more rain and slightly stronger wind during the winter. The yearly cycle looks much the same between locations and these trends should help me to plan trips to capture the kite photographs I will need.

Possible Project Locations

For my MSc visualisation project I aim to make short film using aerial reconstruction to tell the story of a historical site.

View Jarshof on a Larger Map

Jarshof is my first choice. The site dates from 2,500 BC and is layered with a complex chronology including Bronze Age houses, an Iron Age broch and a Viking settlement among more recent structures. The Iron age portion has been dramatically eroded by the sea and it was here where the site was uncovered after storm erosion in the late 1800s. The stories surrounding the site make it an attractive choice to base my film around.

Zoom out a little on the map and you will notice that Jarlshof lies around 300m from the end of the runway at Sumburgh Head airport, making it effectively a no fly zone for kites.

Problem. I'm pursuing the possibility of CAA permission to fly kites at the site as well a pole photography and other low level photography options. Failing this I can go for my second option:

View Gurness on a Larger Map

Gurness is a 2000 year old ruined broch village site. The exposed remains of the walls and outer ditches could be well illustrated from above.

The benefit of using broch sites is that with over 500 known sites across Scotland there is the opportunity to synthesize photographs and geometry from a complete broch to aid the re-construction of a ruined site.

Tuesday, 11 October 2011

St Bridget's Kirk Commission

This kite photograph was commissioned by Historic Scotland for a new interpretation panel on the Fife Coastal Path which runs behind the church in Dalgety Bay. The brief was to illustrate the coastline's proximity to the graveyard, a connection which is important to the kirk's history. A difficult location with trees and tides to deal with but a pleasing result. I have passed on ownership of the image and it is reproduced here by kind permission of Historic Scotland © 2011.

Friday, 7 October 2011

Tealing Earthhouse

This 2000 year old storage cellar would have been part of a larger roundhouse built above ground. Situated in Tealing just outside of Dundee it presents the same challenges for KAP and photogrammetry which I expect to face capturing other Iron Age ruins, the biggest being overhanging walls. I shot around 2000 frames this evening which I'll attempt to resolve into 3D at a later date. Details of the site here.

Wednesday, 5 October 2011

Aerial Inspiration

The film 'Home', among other work by Yann Arthus-Bertrand, is a great example of where aerial perspectives can bring a sense of reflection and global unity to an audience. His images are both illustrative and emotive relating human interactions with a landscape which is often vast and alien looking from above.

There is a strong element of simple truth-telling in his work which gives it some extent of universal appeal. Despite this his later work has become increasingly politically strategical. He is a vocal ecological activist and founded the umbrella organisation which is concerned with climate change issues and the protection of biodiversity.

Home was released for free and can be streamed here.

Saturday, 1 October 2011

Photogrammetry tests

Some experiments with photogrammetry software using a sequence of 33 kite photographs of Callanish Standing Stones, taken back in 2007.

This is a Maya render of geometry generated by Arc3D. It took around an hour to resolve on their servers. It has missed a couple of the thinner standing stones but overall I'm impressed by the detail, particularly on the ground and the ruined burial chamber in the center.

Photosynth turned the same image sequence into this cloud of around 50,000 points. These results look more thorough but will require a tool to convert the points into a mesh for Maya.

Perhaps the best results from Autodesk Photofly with mesh generation (this one is only draft quality) and the very nice faeture that it projects the photographs onto the UV map automatically. Next to run it on a fast enough windows PC to generate a high quality mesh. These three images are Maya renders of the Photofly mesh.